Biologically generated fiee radicals have been implicated in a large number of disease states. The survival of aerobic organisms in an oxygen environment involves a complicated interplay between the biological generation of these very reactive chemical species and the ability of the organism to control them (Del Maestro RF, Acta Phy Scan Suppl. 492:153-68 (1980)). This interplay between the host organism and biologically generated flee radicals results in profound biochemical alterations which culminate in cellular injury and death of the organism. The accumulated products of free radical reactions result in some of the large number of disease conditions which have been suggested to result, in part, from cellular injury induced by an increased flux of intracellular free radicals. These include, but are not limited to cancers, cardiovascular disease, central nervous system disorders, bone disease, aging, Alzheimer's dementia, inflammatory disorders, rheumatoid arthritis, autoimmune diseases, respiratory distress and emphysema.
The association of free radical damage with many disease states is well documented and many cellular constituents, including enzymes, ion channels, structural proteins and membrane lipids are potential targets for reactive free radical species (Rice-Evans C, Mol Aspects of Med 13(1):1-111 (1992)). The antioxidant status at the appropriate site will limit the damage. Free radical reaction with these potential targets may compromise a range of cellular functions leading to pathological change and ultimately cell death. The antioxidant status at the potential reaction site will limit damage. Antioxidants play an important role in protecting DNA, proteins (including lipoproteins) and membrane lipids against oxidative damage.
There is strong evidence that free radical damage contributes to the etiology of many chronic health problems. For most human diseases, oxidant formation from endogenous sources is secondary to the initial disease process, but oxidative damage exacerbates the primary lesion. For example, reperfusion injury can be defined as the damage that occurs to an organ during the resumption of blood flow following an episode of ischemia Oxygen restoration, although necessary, causes increased oxidant formation in the damaged tissue and temporarily worsens the injury (Uraizee A, Circulation 75(6):1237-1248 (1987)). The decline in the antioxidant defenses in the hypoxic myocardium followed by an increase in lipid peroxidation upon reoxygenation was documented by Guanieri (Biochim-Biophys-ACTA 718(2):157-164 (1982)). In reperfusion injury, the infatory response at the site of injury on the endothelium after the ischemic insult generates superoxide from adhesion and activation of neutrophils. In a number of different clinical conditions, the production of oxygen free radicals in the liver is also increased. In viral hepatitis and in chronic active hepatitis, a high number of stimulated macrophages accumulate in the liver, and they produce free radicals. A large number of toxic chemicals cause toxic liver injury, due to increased free radical generation in the liver, frequently mediated by the cytochrome P450. It can be concluded that hydroxyl radical formation catalyzed by iron released from ferritin is a mechanism incidental to many liver diseases (Lee WM, N Eng J of Med; Review P.1118 (1995)).
Oxidation and the use of antioxidants is also important for the treatment of numerous inflammatory disease states. Rheumatoid arthritis (RA) is the most common chronic inflammatory disease. Epidemiological studies reveal a prevalence rate of classical and definite RA between 0.3 and 1.5 percent. Joint disease with chronic persistent inflammation is accompanied by the formation of H.sub.2 O.sub.2 in the inflamed rheumatoid joint. During inflammation, oxygen free radicals are also produced, especially by polymorphonuclear leukocytes (PMN) and macrophages. In any chronic or acute inflammatory disease, PMN and macrophages will produce both O.sub.2 --and H.sub.2 O.sub.2. Tuberculosis, psoriasis, systemic lupus erythematosus, other autoimmune diseases, and adult respiratory distress syndrome can also be mentioned as inflammatory diseases with oxidation as a contributor, and many others can be added to this list.
The generation of oxygen radicals and the process of lipid peroxidation have also become a focus of attention for investigators in the fields of central nervous system (CNS) trauma and stroke (e.g., ischemia). Numerous studies have provided considerable support for the occurrence of free radical and lipid peroxidation reactions in the injured or ischemic CNS (Hall ED, J-Neurotrauma 9(Suppl. 1):S165-S172 (1992)).
Antioxidants have been suggested to be protective against breast cancer and other cancers including those of the brain and liver, as well as to protect against cardiovascular disease and osteoporosis (Wiseman H, Free Radical Res 21(3):187-94 (1994)). They have been demonstrated to protect model and cellular membranes including the nuclear membrane against potentially carcinogenic free radical intermediates and the products of lipid peroxidation. Severe complications associated with atherosclerosis and its common incidence have focused attention on prevention and therapy of this vascular disease state, possibly through their ability to protect low density lipoproteins (LDL) against oxidative damage (Steinberg D, N Engl J of Med 14:915-924 (1989)).